We introduce the Ante framework to automate the evaluation of student tests in such a way that students will see them as an integral part of the software development process. Our unique approach is to evaluate student testing before students are allowed to submit implementations of the assignment. By evaluating student testing, we can ensure that 1) students understand the assignment before moving on to implementing it and 2) students have a set of tests to aid in implementing their assignment. In this paper we will describe the existing tools and techniques to evaluate student testing, discuss the process of utilizing this framework from both the student and instructor points of view, describe the technical and usability issues in crafting Ante, and report preliminary feedback of student attitudes towards testing in the context of this new paradigm.

When properly constructed, a modular multimedia system can satisfy a client's request in multiple ways by using different sequences of modules and by reusing existing streams within the system. Such flexibility in a multimedia server or proxy can provide a rich set of services to clients while efficiently utilizing system resources by choosing the best way to schedule (i.e. allocate resources for) new clients. However, it is difficult to optimally schedule clients in an online fashion as the problem is NP-complete. In this paper, we provide an efficient online algorithm to schedule client requests using a modular multimedia platform.

We present the design, implementation, and performance evaluation of AMPS --- a flexible, scalable proxy testbed that supports a wide and extensible set of next-generation proxy streaming services. AMPS employs a modular architecture and is built on top of a commodity Linux system. We study the performance of AMPS proxy using a server-proxy-client configuration in a switched-Gigabit LAN environment. We identify the CPU to be the system bottleneck. Through profiling study, we further identify the kernel network protocol processing and the Network Reception Module inside the proxy to be the most CPU-intensive components. We also quantify the maximum achievable throughput for two of the principal components of the proxy - the control plane and data plane, and characterize the end-to-end performance along the server-to-proxy-to-client path. We discuss lessons learned and the various optimizations made in the course of our study to improve system performance.

In recent years there has been considerable research on new distributed hash tables (DHTs), improvements on existing DHTs, and DHT-enabled systems. However, little of it focuses on their differences [M. Castro et al., 2002]. To this purpose we introduce a simple modeling framework that allows us to mathematically model the search costs of most classes of DHTs. To illustrate the usefulness of this framework, we examine a class of DHTs, which includes tapestry and pastry, that we call dynamic PRR meshes (DPMs). In particular we examine how planned object duplication (POD) strategies affect the search costs of DPMs that employ them. We introduce 3 new DPMs that employ different POD strategies and compare them with the POD strategies that tapestry and pastry use. Through our model we discover cyclic behaviors in search costs over the number of nodes present in the DPM, the effects of variability in the underlying network and provide comparisons of the performance of all 5 DPMs.

Multimedia streaming applications can consume a significant amount of server and network resources. Periodic broadcast and patching are two approaches that use multicast transmission and client buffering in innovative ways to reduce server and network load, while at the same time allowing asynchronous access to multimedia steams by a large number of clients. Current research in this area has focussed primarily on the algorithmic aspects of these approaches, with evaluation performed via analysis or simulation. In this paper, we describe the design and implementation of a flexible streaming video server and client testbed that implements both periodic broadcast and patching, and explore the issues that arise when implementing these algorithms. We present measurements detailing the overheads associated with the various server components (signaling, transmission schedule computation, data retrieval and transmission), the interactions between the various components of the architecture, and the overall end-to-end performance. We also discuss the importance of an appropriate server video segment caching policy. We conclude with a discussion of the insights gained from our implementation and experimental evaluation.

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